An arrangement with a lever of the kind specified is described in the specifications of U.S. Pat. No. 4,723,642 and the corresponding French published patent application No. FR 2 575 707A. That document discloses an upstream lever part which has a projecting contact element associated with electrical contact zones of the sensors, so that this contact element makes electrical contacts. It also discloses arrangements which use a coil spring and articulating devices. These arrangements involve clearances such that the force threshold may vary over a period of time. In addition, manufacturing tolerances have to be taken into account.
To overcome this drawback, it is possible to use blocks of suitable resilient material to take the place of the coil springs. However, that arrangement is also unsatisfactory because the characteristics of the resilient material change over a period of time. In addition, the resilient blocks are liable to dispersion effects during manufacture.